This MCQ module is based on: Phases of the Moon, Eclipses and ISRO Missions
TOPIC 45 OF 46
Phases of the Moon, Eclipses and ISRO Missions
🎓 Class 7
Science
CBSE
Theory
Ch 12 — Earth, Moon and the Sun
⏱ ~14 min
🌐 Language: [gtranslate]
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Anaya Counts the Moon's Shapes
Every evening for a month, Anaya of Varanasi stepped onto her terrace after dinner and sketched the Moon in her diary. On the night of Amavasya she could not find the Moon at all — the sky was a sheet of dark velvet. Over the next fortnight her sketches showed a thin crescent, a fat curved half, a lopsided gibbous, and finally a perfect silver disc on Purnima. Then the Moon began shrinking again, night after night, until it vanished once more.
Her grandmother said, "The Moon never really changes shape, beti. What changes is how much of its lit side we can see from Earth. The calendar your grandfather follows — with Ekadashi, Amavasya, Purnima — is built around exactly this rhythm."
Think first: The Moon does not make its own light. So what is lighting it up? And why would the same lit ball look like different shapes from our window, night after night?
12.10 The Moon's Two Motions
Like Earth, the Moon also has two motions. It rotates on its own axis, and it revolves around the Earth. Remarkably, the Moon takes almost the same time to rotate once as it does to revolve once around Earth — about 27.3 days. This perfect match is called tidal locking, and it means we always see the same face of the Moon from Earth. The "far side" of the Moon was never photographed by humans until space missions.
12.11 Why the Moon Has Phases
The Moon has no light of its own. Only the half facing the Sun is ever lit; the other half is dark. As the Moon revolves around Earth, we on Earth view this lit half from different angles. The shapes we see are called phases of the Moon.
The Eight Phases
1. New Moon
(Amavasya)
(Amavasya)
2. Waxing Crescent
3. First Quarter
4. Waxing Gibbous
5. Full Moon
(Purnima)
(Purnima)
6. Waning Gibbous
7. Last Quarter
8. Waning Crescent
Waxing means the lit portion is growing each night (from new toward full). Waning means it is shrinking (from full back to new). The full cycle from one New Moon to the next takes about 29.5 days. This period is called a synodic month, and it forms the basis of the traditional Hindu lunar calendar. Festivals like Holi (Purnima), Diwali (Amavasya) and Karwa Chauth (Purnima) are scheduled by this Moon cycle.
Amavasya — the dark, no-Moon night. Purnima — the full-Moon night. These Sanskrit terms appear in every Panchang (Indian almanac).
12.12 Solar and Lunar Eclipses
An eclipse happens when the Sun, Earth and Moon line up in a particular way, and the shadow of one body falls on another.
Solar Eclipse (Sun in shadow)
When the Moon comes exactly between the Sun and Earth, it blocks the Sun's light for viewers standing in its shadow. This only happens on a New Moon day, but not every New Moon — the three bodies must line up precisely. During a total solar eclipse, the sky darkens in the middle of the day. Never look at a solar eclipse with naked eyes — use special eclipse glasses or a projection method.
Lunar Eclipse (Moon in shadow)
When Earth comes between the Sun and the Moon, Earth's shadow falls on the Moon. This happens only on a Full Moon night, and even then only when the alignment is exact. A lunar eclipse is completely safe to watch; the Moon often turns a coppery-red colour because some red light bends through Earth's atmosphere and reaches its surface.
| Feature | Solar Eclipse | Lunar Eclipse |
|---|---|---|
| Who comes in between? | Moon, between Sun & Earth | Earth, between Sun & Moon |
| Moon phase | New Moon (Amavasya) | Full Moon (Purnima) |
| Seen from | A narrow strip of Earth | The whole night-side of Earth |
| Safe to look at? | No — use filters | Yes — fully safe |
12.13 Aryabhata — India's Early Astronomer
Long before telescopes existed, Indian scholars were mapping the sky using careful observation and mathematics. The most famous of them is Aryabhata (476–550 CE), who worked at the ancient university of Nalanda. In his book Aryabhatiya, written when he was only 23, he made claims that were astonishing for his time:
- Earth is a sphere that rotates on its own axis, making day and night.
- Eclipses are caused by shadows of Earth and Moon — not by mythical demons.
- He calculated the length of the year to about 365.25 days — extremely close to the modern value.
- He gave an accurate value of π (pi) and important ideas in algebra and trigonometry.
Other great Indian astronomers include Brahmagupta (7th century), Bhaskara I & II, and Varahamihira. India's respect for Aryabhata is so deep that the country's very first satellite, launched in 1975, was named after him.
12.14 ISRO — India's Space Journey Today
The Indian Space Research Organisation (ISRO) has carried Aryabhata's spirit into the 21st century with remarkable missions exploring the Moon, Mars and the Sun.
Chandrayaan-1 (2008)
India's first Moon mission. Orbited the Moon and made a historic discovery — water molecules on the lunar surface.Chandrayaan-2 (2019)
Sent an orbiter, lander (Vikram) and rover (Pragyan). The orbiter continues working perfectly; the lander had a rough landing but the orbiter is still studying the Moon.Chandrayaan-3 (2023)
Made India the first country ever to soft-land near the Moon's south pole on 23 August 2023 — now celebrated as National Space Day. The Pragyan rover walked on lunar soil.Mangalyaan / Mars Orbiter Mission (2013)
India became the first country in the world to reach Mars on its very first attempt, and did it at a fraction of the cost of other Mars missions.Aditya-L1 (2023)
India's first space-based mission to study the Sun. It now orbits a special point in space called L1, about 1.5 million km from Earth, from where it watches the Sun continuously.Activity 12.3 — A Ball & Lamp Moon-Phase ModelL3 Apply
What you need: a tennis ball (Moon), a bright table lamp (Sun), a dark room, your head (Earth!).
What to do:
- Place the lamp on a table with its bulb facing you — this is the Sun.
- Hold the ball in your hand, arm stretched forward, between you and the lamp. Look at how much of the ball's lit half you can see. (This is the New Moon position.)
- Turn slowly to the left, keeping the ball at arm's length. Stop at quarter turns.
- Observe the ball at each turn and note the shape of its lit part.
Predict: At which position will the whole lit half of the ball face you, giving a "Full Moon"?
When the ball is directly opposite the lamp (behind your back and held up so your own head doesn't cast a shadow on it), the entire lit half faces you — the Full Moon. At 90° turns you see a half-lit ball (First Quarter and Last Quarter). When the ball is between you and the lamp, you see only its dark side — the New Moon. The phases really come from nothing more than changing viewing angles.
Competency-Based Questions Mixed L2–L4
Scenario: Anaya's grandfather announces that a total lunar eclipse will be visible from Varanasi on the next Purnima night. Anaya is excited and gets her binoculars ready. Her brother Rohan warns her, "Wait — aren't eclipses dangerous to watch?"
Q1. The Moon takes about how many days to revolve once around the Earth?
(c) About 27 days (more precisely 27.3 days for one revolution; 29.5 days for a full phase cycle).
Q2. Which of the following is correct about the Moon?
(b) It reflects sunlight. The Moon is just a ball of rock; it shines only because it bounces the Sun's light back to us.
Q3. Is Rohan right to worry about watching a lunar eclipse? Explain.
No. A lunar eclipse is completely safe to watch with naked eyes or even with binoculars/telescopes, because we are only looking at the darkened Moon, not the Sun. It is solar eclipses that are dangerous — during those, looking directly at the Sun can permanently damage the eyes, so special eclipse filters are required.
Q4. Fill in the blanks: A solar eclipse can occur only on __________, whereas a lunar eclipse can occur only on __________.
A solar eclipse can occur only on Amavasya (New Moon), and a lunar eclipse can occur only on Purnima (Full Moon).
Q5. Why was Chandrayaan-3's 2023 landing considered historic for India? L4
India became the first nation in the world to soft-land a spacecraft near the south pole of the Moon — a region never reached before because of its rough terrain. The Pragyan rover then explored the area for the first time. This achievement is now remembered each year on 23 August as National Space Day.
Assertion & Reason L4 Analyse
Choose: (A) Both A and R true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
A: We always see the same face of the Moon from Earth.
R: The Moon takes nearly the same time to rotate on its axis as it takes to revolve once around Earth.
(A) — this matching is called tidal locking. Because both motions have the same period (~27.3 days), the same hemisphere always points toward Earth.
A: A solar eclipse does not happen every new Moon.
R: The Moon's orbit is slightly tilted compared to Earth's orbit around the Sun, so the three bodies line up exactly only sometimes.
(A) — the tilt of the Moon's orbit means that on most new Moons its shadow misses Earth, so eclipses happen only a few times a year.
A: Aryabhata believed eclipses were caused by demons swallowing the Sun or Moon.
R: He worked before modern science existed.
(D) — A is false; Aryabhata actually rejected the demon explanation and correctly said eclipses are shadows. R is true but does not support the false assertion.
Frequently Asked Questions — Phases of the Moon, Eclipses and ISRO Missions
What does the topic 'Phases of the Moon, Eclipses and ISRO Missions' cover in Class 7 Science?
The topic 'Phases of the Moon, Eclipses and ISRO Missions' is part of NCERT Class 7 Science Chapter 12 — Earth, Moon, and the Sun. It covers the key ideas of phases of moon, new moon, full moon, solar eclipse, lunar eclipse, ISRO, Chandrayaan, explained through everyday examples, labelled diagrams and hands-on activities drawn from the NCERT Curiosity textbook. Students learn not just definitions but also the reasoning behind each concept so they can answer competency-based questions and assertion–reason items. The lesson helps Class 7 students build a strong base for higher classes by linking each idea to real observations at home, school and in nature, and by preparing them for CBSE school assessments and Olympiads.
Why is 'Phases of the Moon, Eclipses and ISRO Missions' important for Class 7 NCERT Science?
'Phases of the Moon, Eclipses and ISRO Missions' is important because it builds core scientific thinking that Class 7 students will use throughout middle and secondary school. NCERT Chapter 12 — Earth, Moon, and the Sun — introduces phases of moon and related ideas that appear again in Class 8, 9 and 10 Science. Mastering this subtopic helps students read labels and safety signs, understand news about science and technology, and perform better in CBSE school exams. The chapter also encourages curiosity and evidence-based thinking — skills that support the National Education Policy (NEP) 2020 focus on conceptual understanding and competency-based learning.
What are the key concepts students should remember from Phases of the Moon, Eclipses and ISRO Missions?
The key concepts in 'Phases of the Moon, Eclipses and ISRO Missions' for Class 7 Science are: phases of moon, new moon, full moon, solar eclipse, lunar eclipse, ISRO, Chandrayaan. Students should be able to define each term in their own words, give at least one everyday example, and explain how the concept connects to other chapters in NCERT Class 7 Science. For example, linking the idea to daily life — in the kitchen, classroom or outdoors — makes revision easier. Writing short notes, drawing labelled diagrams and solving the NCERT in-text and exercise questions for Chapter 12 will help students retain these concepts for unit tests and the annual CBSE examination.
How is Phases of the Moon, Eclipses and ISRO Missions taught using activities in NCERT Curiosity Class 7?
NCERT Curiosity Class 7 Science teaches 'Phases of the Moon, Eclipses and ISRO Missions' using an inquiry-based approach with Predict–Observe–Explain activities. Students are asked to make a guess first, then perform a simple experiment with safe, easily available materials, and finally explain what they observed. This matches the NEP 2020 focus on learning by doing. For Chapter 12 — Earth, Moon, and the Sun — the textbook includes hands-on tasks, labelled diagrams and questions that build Bloom's Taxonomy skills from Remember (L1) to Create (L6). Teachers use these activities, along with competency-based questions (CBQs) and assertion–reason items, to check real understanding rather than rote memorisation.
What real-life examples of phases of moon can Class 7 students observe at home?
Class 7 students can observe phases of moon at home in many simple ways linked to 'Phases of the Moon, Eclipses and ISRO Missions'. Kitchens, school bags, playgrounds and the night sky are full of examples that connect to NCERT Chapter 12 — Earth, Moon, and the Sun. For instance, students can check labels on food and cleaning products, watch changes while cooking, or observe the Sun and Moon across a week. Keeping a small science diary — noting the date, what was observed and a quick sketch — turns everyday life into a science lab. These real-life connections make concepts stick and prepare students well for competency-based questions in CBSE Class 7 Science.
How does 'Phases of the Moon, Eclipses and ISRO Missions' connect to other chapters of Class 7 Science?
'Phases of the Moon, Eclipses and ISRO Missions' connects to many other chapters in NCERT Class 7 Science Curiosity. The ideas of phases of moon appear again when students study related topics like heat, light, changes, life processes and Earth-Sun-Moon. For example, understanding this subtopic helps in building mental models for later chapters and for Class 8, 9 and 10 Science. Teachers often use cross-chapter questions in CBSE examinations to test whether students can apply what they learned in Chapter 12 — Earth, Moon, and the Sun — to new situations. This integrated approach matches the NEP 2020 and NCF 2023 focus on holistic, competency-based learning.
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